1. Field of Invention
The current invention relates to the diagnosis, treatment, and therapy monitoring for vestibule-ocular reflex (VOR) dysfunction.
2. Discussion of Related Art
The vestibular system is integral to balance control. The paired vestibular organs, housed within the temporal bone, include three orthogonal semicircular canals (superior, posterior, and horizontal) and two otolith organs (the utricle and saccule). Together, the semicircular canals and otolith organs provide continuous input to the brain about rotational and translational head motion and the head's orientation relative to gravity. This information from the vestibular organs and their central pathways allows for the maintenance of gaze and postural stability via the vestibulo-ocular reflex and vestibulospinal reflex, respectively. Dysfunction of the peripheral vestibular structures cannot be directly observed but can be inferred from assessment of these reflexes (e.g., with caloric reflex test).
Vestibular dysfunction is typically characterized by vertigo (i.e., an illusory sense of motion) and imbalance owing to disturbances in gaze and postural stability. In some cases, vestibular dysfunction can culminate catastrophically in a fall, which is associated with serious injury and restricted mobility and ranks among the leading causes of death among older individuals. The costs of increased needs and diminished autonomy associated with falls also exert a tremendous societal toll.
Vestibular dysfunction is common among adults in the United States. The National Institute of Health (NIH) estimates that over 90 million Americans, age 17 and older, have experienced a dizziness or balance disorder. Data has established that approximately 53% of patients with inner ear disorders have a costly fall. The non-profit Vestibular Disorders Association reports 37,800 requests per month to locate physicians, physical therapists, and audiologists who specialize in vestibular disorders. The expectation is that balance and dizziness problems in the United States will continue to demand significant hospitalization and treatment costs. These data suggest the importance of diagnosing, treating, and potentially screening for vestibular deficits to reduce the burden of fall-related injuries and deaths in the United States.
The main function of the vestibulo-ocular reflex (VOR) is to stabilize visual images on the retina during head rotations. Gaze stability is defined as the ability to see clearly during head motion, and is the unique function of the VOR. In individuals with a normal VOR, visual acuity during head movements typical of daily activities is similar to that measured with the head stationary. In contrast, individuals with abnormal vestibular (inner ear) systems (reduced VOR) report visual images appear to move when their heads are moving. As a result, individuals with reduced VOR have visual image motion on their retinas, resulting in a degradation of visual acuity during head movements.
Traditional and current commercial products only measure acuity when the subject self-induces a head motion. Traditional and current rehabilitation asks patients to move their head while focusing on targets, in an attempt to improve patients' ability to see clearly during head rotation. Although the effectiveness of the available diagnosis and rehabilitation is established, there is a need in the art for improved diagnosis and rehabilitation for VOR dysfunction.